Many industrial and commercial buildings have the burden of illuminating large areas from standard height as well as from higher than normal ceilings. One solution to this lighting application has been the use of high intensity discharge lamps. Mercury vapor, sodium and other high intensity discharge lamps in commercial applications may consume as much as 400 to 1000 watts, and generate an associated amount of heat, contributing to additional heating, ventilating and air conditioning (“HVAC”) operation and fire protection considerations.
These lamps also utilize a certain time duration to warm up and achieve full illumination capability, resulting in time periods with less than desired lighting coverage. Such high intensity discharge lamps are also relatively expensive costing several hundreds of dollars per lamp.
Lamp manufacturers are constantly looking for ways to maximize the amount of foot candles of illumination which can be generated for a fixed amount of power consumption or wattage. These objectives have resulted in the evolution of high intensity discharge lamps which burn metallic vapors to achieve high lumen output.
A fairly common discharge lamp with a reflective lamp is disclosed in U.S. Pat. No. 6,291,936 B, issued Sep. 18, 2001 to MacLennan et al. Summarizing, the MacLennan patent discloses a discharge lamp including an envelope, a source of excitation power coupled to the fill for excitation thereof and thereby emit light, a reflector disposed around the envelope and defining an opening, and a reflector configured to reflect some of the light emitted by the fill back into the fill while allowing some light to exit through the opening. This description is typical of a high intensity discharge lamp. The high pressure sodium lamp emits the brightest light while metal halide and mercury vapor lamps emit about the same amount of light. For a lamp in the 400 W range, for example, a ballast which acts as the excitation for the fill may typically consume 40 to 58 watts.
Fluorescent lamps are also used in commercial applications, often in offices and warehouses where a plurality of fluorescent tubes are positioned in front of a washboard-shaped, mirrored reflector. The purpose of the reflector is to reflect the light emitted upward back down toward the targeted illumination area. Fluorescent lamps differ from high intensity discharge lamps in that the “strike” time (the time to excite the interior of the lamp) is short—almost immediate, where the high intensity discharge lamps must warm up to full illumination. Fluorescent lamps also operate at a cooler temperature than do high intensity discharge lamps. The same approach may be applied to retrofitting existing installations in the commercial office environment.
Fluorescent lamps are also used in residential applications. A growing trend is the replacement of incandescent lamps with fluorescent lamps to achieve not only brighter light, but also savings in power consumption.
Lamps like the Sylvania ICETRON lamp are touted as having a 100,000 hour lamp life, or roughly five times the life of a standard high intensity discharge lamp. Consequently, with such added lamp life, the amount of maintenance required to change lamps in order to maintain illumination is reduced by 80%.
When one examines the shortcomings attendant to the use of high intensity discharge lamps and the advantages of fluorescent lamps, several observations result. By comparison, fluorescent lamps provide crisp white light in comparison to high intensity discharge lamps which offer unpleasant color and distracting color shift. Fluorescent lights may also be flexibly dimmed whereas high inensity discharge lights may not be operated below 50% output.
What is needed is a lamp which can illuminate a target area with the same amount of foot candles as a high intensity discharge lamp without consuming the same amount of energy, without requiring a warm-up period, and in operation generating less heat.
There exists a further need for high intensity discharge lamps which can illuminate a target area with the same amount of foot candles as a higher wattage, high intensity discharge lamp without consuming the same amount of energy.
Also, what is needed is a lamp which can illuminate a target area with the equivalent of foot candles as an incandescent lamp, but without consuming the same amount of energy.
Further, if the illuminating capability of a high intensity discharge lamp could be accomplished without the high capital cost associated with the purchase and operation of such lamps, the relative operating cost of illuminating industrial and commercial buildings would be reduced. The same can be said for the improvement of residential illuminations as well.
If such a lamp as described immediately above were developed, the cost of retrofitting fixtures with such lamps would be paid for relatively quickly by the associated savings from reductions in energy consumption.
One area of the art that remains to be fully developed is the optimal use of reflective surfaces to assist in directing light which would normally travel away from the targeted illumination area.